U.S. patent application number 11/105791 was filed with the patent office on 2006-10-19 for coated lead fixation electrode.
This patent application is currently assigned to Cardiac Pacemakers, Inc.. Invention is credited to Ronald W. JR. Heil, Michael T. Nelson.
Application Number | 20060235499 11/105791 |
Document ID | / |
Family ID | 37011925 |
Filed Date | 2006-10-19 |
United States Patent
Application |
20060235499 |
Kind Code |
A1 |
Heil; Ronald W. JR. ; et
al. |
October 19, 2006 |
Coated lead fixation electrode
Abstract
In one embodiment, the present invention provides a cardiac lead
including a fixation member extending from a distal end of the
lead. The fixation member includes a coated portion and an uncoated
portion. The coating that forms the coated portion includes a
biocompatible polymer material and a therapeutic agent. The coating
may provide for the delivery of the therapeutic agent directly at
the sight of fixation for an extended period of time.
Inventors: |
Heil; Ronald W. JR.;
(Roseville, MN) ; Nelson; Michael T.; (White Bear
Lake, MN) |
Correspondence
Address: |
GUIDANT PATENT DOCKETING;FAEGRE & BENSON, LLP
2200 WELLS FARGO CENTER
90 SOUTH SEVENTH STREET
MINNEAPOLIS
MN
55402-3901
US
|
Assignee: |
Cardiac Pacemakers, Inc.
St. Paul
MN
|
Family ID: |
37011925 |
Appl. No.: |
11/105791 |
Filed: |
April 14, 2005 |
Current U.S.
Class: |
607/127 |
Current CPC
Class: |
A61N 1/0575 20130101;
A61N 1/0568 20130101 |
Class at
Publication: |
607/127 |
International
Class: |
A61N 1/05 20060101
A61N001/05 |
Claims
1. A lead for use in a cardiac rhythm management system, the lead
comprising: a lead body including a proximal end and a distal end
and a conductive member extending between the proximal and distal
ends; a fixation electrode coupled to the lead body and in
electrical communication with the conductive member; and a
biocompatible coating applied over a portion of the fixation
electrode, the coating including a polymeric material and a
therapeutic agent.
2. The lead of claim 1 wherein the fixation electrode includes a
coated portion and an exposed portion.
3. The lead of claim 2 wherein the coated portion covers a proximal
portion of the fixation electrode.
4. The lead of claim 2 comprising a plurality of alternating coated
and exposed portions.
5. The lead of claim 1 wherein the fixation electrode comprises a
positive fixation electrode.
6. The lead of claim 1 wherein the fixation electrode comprises a
helical or coiled portion.
7. The lead of claim 1 further comprising a polymer sleeve disposed
over a portion of the fixation electrode, and wherein the coating
is applied onto a portion of the polymer sleeve.
8. The lead of claim 1 wherein the polymeric material is
substantially insoluble in water.
9. The lead of claim 1 wherein the polymeric material comprises
silicone.
10. The lead of claim 1 wherein the therapeutic agent comprises a
steroid.
11. The lead of claim 10 wherein the steroid is selected from the
group consisting of dexamethasone, betamethasone, paramethasone,
beclomethasone, clobetasol, triamcinolone, prednisone, prednisolone
and combinations and derivatives thereof.
12. The lead of claim 10 wherein the therapeutic agent comprises an
ester of a steroid.
13. The lead of claim 10 wherein the therapeutic agent comprises an
acetate, diacetate, propionate, dipropionate, cypropionate,
butyrate, acetonide, hexacetonide, succinate or valerate ester of a
steroid.
14. The lead of claim 13 wherein the therapeutic agent comprises an
acetate ester of dexamethasone and the polymeric material comprises
silicone.
15. The lead of claim 1 wherein the coating includes a first layer
comprising a first coating mixture and a second layer comprising a
second coating mixture.
16. A cardiac rhythm management system comprising a pulse
generator; a lead having an electrode and a proximal end adapted
for coupling with the pulse generator; a coating means for
providing an extended release of a anti-inflammatory therapeutic
agent, the coating means being disposed over a portion of the
electrode; and means for affixing the lead in a patient.
17. A method of coating a cardiac lead electrode comprising:
providing a coating mixture including a polymeric material and a
therapeutic agent; applying the coating mixture onto the electrode
such that the electrode includes a coated portion and an exposed
portion; and treating the coating mixture to form a coating on the
electrode.
18. The method of claim 17 wherein the coating mixture is applied
to the electrode by spraying, brushing or dipping.
19. The method of claim 17 wherein the electrode includes a polymer
sleeve, and the coating mixture is applied onto the polymer
sleeve.
20. The method of claim 19 wherein a portion of the polymer sleeve
is removed after applying the coating mixture to provide the coated
and exposed portions.
21. The method of claim 17 further comprising the steps of masking
a portion of the electrode prior to applying the coating mixture,
and de-masking the portion of the electrode after applying the
coating mixture to provide the exposed portion.
22. The method of claim 17 wherein the treating step comprises
drying the coating mixture, curing the coating mixture, or both.
Description
TECHNICAL FIELD
[0001] The present invention relates to cardiac rhythm management
systems, and in particular to mechanisms for improving the
performance of cardiac leads implanted in a patient's vascular
system.
BACKGROUND
[0002] When functioning properly, the human heart maintains its own
intrinsic rhythm, and is capable of pumping adequate blood
throughout the body's circulatory system. However, some people have
irregular cardiac rhythms, referred to as cardiac arrhythmias. Such
arrhythmias result in diminished blood circulation. One manner of
treating cardiac arrhythmias includes the use of a cardiac rhythm
management system. Such systems may be implanted in a patient to
deliver electrical pulses to the heart.
[0003] Cardiac rhythm management systems include, for example,
pacemakers (also referred to as "pacers"), defibrillators (also
referred to as "cardioverters") and cardiac resynchronization
therapy ("CRT") devices. These systems use conductive leads having
one or more electrodes to deliver pulsing energy to the heart, and
may be delivered to an endocardial, epicardial and myocardial
position within the heart.
[0004] Unfortunately, interactions between the electrode and the
adjacent tissue in the heart may vary the stimulation thresholds of
the tissue over time. This variation may be caused by the formation
of fibrotic scar tissue during the recovery and healing process as
the body reacts to the presence of the electrode. The formation of
fibrotic tissue may result in chronic stimulation energy thresholds
that exceed the acute energy thresholds obtained immediately after
implant. As a result, higher stimulation energies are required,
thereby shortening the usable life of the battery-powered
implantable cardiac rhythm management device.
[0005] There is a need in the art for cardiac leads that deliver
therapeutic agents such as steroids directly to the site at which
the electrode is positioned in order to maintain consistent
stimulation energy thresholds throughout the life of the lead.
SUMMARY OF THE INVENTION
[0006] In one embodiment, the present invention provides a lead for
use in a cardiac rhythm management system. The lead includes a lead
body having a proximal end, a distal end, and a conductive member
extending between the proximal and distal ends. The lead further
includes a fixation electrode coupled to the lead body, which is in
electrical communication with the conductive member. A
biocompatible coating including a polymeric material and a
therapeutic agent is applied over a portion of the fixation
electrode.
[0007] Suitable therapeutic agents include steroids, and in
particular, esters of steroids. Suitable polymeric materials may
generally resist degradation in vivo, and include medical grade
silicone polymers. The combination of the therapeutic agent and
polymeric material may be selected to provide immediate and/or
extended treatment in vivo.
[0008] The coating may be applied to the fixation electrode in
order to provide the electrode with discrete coated and exposed
portions. For example, the distal end of the electrode may remain
exposed, while the proximal end is coated. In another example,
alternating exposed and coated portions may be utilized. In a
further example, the coating is applied onto a polymer sleeve
disposed over a portion of the electrode. Suitable polymer sleeves
may act as a substrate to receive the coating and/or as an
insulator over portions of the fixation electrode.
[0009] In another embodiment, the present invention provides a
cardiac rhythm management system including a pulse generator, a
lead having an electrode and a proximal end coupled to the pulse
generator, and a coating means disposed over a portion of the
electrode for providing an extended release of an anti-inflammatory
therapeutic agent.
[0010] In yet another embodiment, the present invention provides a
method for coating an electrode on a cardiac lead. A coating
mixture including a polymeric material and a therapeutic agent
applied onto the electrode such that the electrode includes a
coated and an uncoated portion. The applied coating mixture may
then be treated, for example by drying and/or curing, to form a
coating on the electrode.
[0011] The coating may be applied in several ways. In one
embodiment, the coating is brushed, sprayed or otherwise applied
onto a portion of the electrode to provide a coated and an exposed
portion. In another embodiment, the coating is applied onto a
polymer sleeve disposed over a portion of the electrode.
Optionally, a portion of the polymer sleeve may then be removed to
provide the electrode with a coated and an exposed portion. In yet
another embodiment, a portion of the electrode is masked prior to
application of the coating mixture. After application of the
coating mixture, the masked portions of the electrode are de-masked
to provide the electrode with a coated and an exposed portion.
[0012] In a further embodiment, the present invention provides a
coating for application to an electrode on a cardiac lead. The
coating includes one or more of the polymeric materials and
therapeutic agents reported herein.
[0013] In yet a further embodiment, the present invention provides
a coating for a medical device, which includes a mixture of a
polymeric material and a lipophilic ester of a steroid, for example
the acetate ester of dexamethasone.
[0014] While multiple embodiments are disclosed, still other
embodiments of the present invention will become apparent to those
skilled in the art from the following detailed description, which
shows and describes illustrative embodiments of the invention. As
will be realized, the invention is capable of modifications in
various obvious aspects, all without departing from the spirit and
scope of the present invention. Accordingly, the drawings and
detailed description are to be regarded as illustrative in nature
and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic illustration of distal portions of the
cardiac rhythm management system implanted in a patient's heart
according to one embodiment of the present invention.
[0016] FIG. 2 is a schematic illustration of the distal end of a
cardiac lead according to one embodiment of the present
invention.
[0017] FIG. 3 is a schematic illustration of the distal end of a
cardiac lead according to one embodiment of the present
invention.
[0018] FIG. 4 is a schematic illustration of the distal end of a
cardiac lead according to one embodiment of the present
invention.
[0019] FIG. 5 is a schematic illustration of the distal end of a
cardiac lead according to one embodiment of the present
invention.
[0020] FIG. 6 is a flow-chart summarizing a method of using
embodiments of the present invention.
[0021] While the invention is amenable to various modifications and
alternative forms, specific embodiments have been shown by way of
example in the drawings and are described in detail below. The
intention, however, is not to limit the invention to the particular
embodiments described. On the contrary, the invention is intended
to cover all modifications, equivalents, and alternatives falling
within the scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION
[0022] FIG. 1 is a schematic drawing of a cardiac rhythm management
system 10 including an implantable cardiac rhythm management device
12 and a lead 14, which electrically couples the cardiac rhythm
management device 12 to a patient's heart 16. The lead 14 includes
a proximal end 18 attached to the cardiac rhythm management device
12 and a distal end 20 which is implanted in the patient's heart
16.
[0023] FIG. 1 further illustrates the chambers of the heart 16,
including a right atrium 22, a right ventricle 24, a left atrium
26, and a left ventricle 28. In the embodiment illustrated in FIG.
1, the lead 14 is an endocardial lead, and the distal end 20 of the
lead 14 extends transvenously through the right atrium 22, through
a coronary sinus 30, and into a great cardiac vein 32. The
illustrated disposition of the lead 14 may be used for delivering
pacing and/or defibrillation energy to the left side of the heart
16, for the treatment of congestive heart failure (CHF) or other
cardiac disorders requiring therapy delivered to the left side of
heart 16.
[0024] FIG. 1 shows in phantom an alternate endocardial disposition
of the lead 14, which extends through the right atrium 22 and/or
the right ventricle 24 and is directly implanted in the endocardium
33. As further shown in phantom in FIG. 1, the lead 14 may also be
directly implanted in an epicardial 34 or myocardial 36 position in
the heart 16. Epicardial and myocardial lead disposition is
generally accomplished by piercing a patient's chest wall and
affixing the lead 14 directly into the epicardium 34 or myocardium
36.
[0025] FIG. 2 shows an enlarged view of the distal end 20 of the
lead 14. A fixation electrode 40 is coupled to the distal end 20 of
the lead 14 such that the fixation electrode 40 is in electrical
communication with the cardiac rhythm management device 12 (See
FIG. 1). The fixation electrode 40 includes a coated proximal
portion 42 and an exposed distal portion 44. The cut-away portion
of FIG. 2 is for illustrative purposes and indicates that the
coated portion 42 comprises a thin coating 46.
[0026] The exposed portion 44 of the fixation electrode 40 is
conductive and is designed to be positively fixed to the desired
site in the heart 16 to deliver current to the heart for cardiac
rhythm management therapy. The coating 46 that forms the coated
portion 42 is designed to release one or more therapeutic agents
directly at the fixation site.
[0027] FIG. 3 shows an alternate embodiment of the present
invention in which the coated portion 42 includes a polymer sleeve
50 positioned over a portion of the fixation electrode 40. The
coating 46 is applied onto the polymer sleeve 50. One benefit to
this configuration is that the polymer sleeve 50 may provide an
improved substrate onto which the coating 46 may be applied, and/or
that the polymer sleeve 50 may also serve as an insulator with
respect to the fixation electrode 40. The polymer sleeve 50 may be
formed from silicone rubber or another biocompatible polymer or
mixture of polymers. In one embodiment, the sleeve has a thickness
of approximately 0.004 in.
[0028] FIG. 4 shows another embodiment of the present invention in
which two coated portions 42 are positioned over discrete proximal
and distal portions of the fixation electrode 40. The exposed
portion 44 is disposed in between the coated portions 42. FIG. 5
shows a further embodiment of the present invention in which the
fixation electrode 40 includes alternating segments of coated
portions 42 and exposed portions 44 to provide several discrete
conductive regions.
[0029] Although FIGS. 2-5 illustrate the fixation electrode as
generally having a coiled or helical shape, a wide variety of
conventional shapes and sizes may also be used for the fixation
electrode 40. Additionally, the relative length of the coated and
uncoated portions 42, 44 shown in FIGS. 3-6, may vary depending on
the particular application. Thus, in certain embodiments coated
portion 42 may make up a majority of the fixation electrode 40. In
other embodiments, the exposed portion 44 may form the majority of
the fixation electrode 40. In yet another embodiment, the coating
46 could be applied to a conventional non-fixation electrode, such
as a ring electrode, to provide coated and uncoated portions 42,
44. In this embodiment, discrete fixation means such as tines,
sutures or other conventional fixation devices could be used to fix
the lead at a desired position.
[0030] The coating 46 generally includes a biocompatible polymer
material and a therapeutic agent. A wide range of biocompatible
polymer materials capable of carrying and delivering a therapeutic
agent may be utilized in embodiments of the present invention. In
one embodiment, the polymer material may remain coated to the
fixation electrode 40 for the life of the lead 14. In another
embodiment, the polymer material may be partially or completely
biodegradable over time. In a further embodiment, the polymer
material may have a low water solubility or may be substantially
water insoluble (collectively referred to herein as "low water
solubility"). In alternative embodiments, the polymer material may
swell when contacted with water or other aqueous mixtures. Suitable
polymeric materials should also be compatible with the therapeutic
agent with which the polymeric material is combined
[0031] Examples of suitable polymer materials include silicone
rubbers, polyurethanes, polyesters, polylactic acids, polyamino
acids, polyvinyl alcohols and polyethylenes. Medical grade silicone
rubbers may be particularly suitable for embodiments of the present
invention.
[0032] Suitable therapeutic agents for incorporation into the
coating 46 may treat the tissue surrounding the fixation site of
the fixation electrode 40, for example by providing an
anti-inflammatory effect, in order to maintain or reduce the
chronic energy thresholds required to provide rhythm management
therapy to the heart 16. Steroids are a broad class of therapeutic
agents that may be suitable for use in embodiments of the present
invention. Examples of suitable steroids include dexamethasone,
betamethasone, paramethasone, beclomethasone, clobetasol,
triamcinolone, prednisone, and prednisolone, as well as
combinations and derivatives thereof. Suitable steroid derivatives
include esters of steroids, such as the acetate, diacetate,
propionate, dipropionate, cypropionate, butyrate, acetonide,
hexacetonide, succinate and valerate esters of such steroids. The
acetate ester of dexamethasone or beclomethasone may be
particularly suitable for certain embodiments. Beclomethasone
dipropionate anhydrous may also be suitable for certain
embodiments. A separate class of therapeutic agents that may be
suitable for certain embodiments include anti-cell proliferation
agents such as paclitaxel (sold as Taxol.RTM. by Bristol-Myers
Squibb) and Docetaxel.RTM. (Rhone-Poulenc Rorer).
[0033] The specific combination of polymer and therapeutic agent,
and the relative concentrations of these materials, may vary
depending on the type of lead implanted, the location of lead
implantation, and the anticipated length of time that the lead is
to remain implanted. In embodiments in which extended treatment
with a therapeutic agent is desired, It may be desirable to utilize
a combination of a polymer and therapeutic agent that provides an
extended release of therapeutic agent. In one embodiment, the
polymer and therapeutic agent may be selected such that the
therapeutic agent generally blends well with, and/or is
substantially soluble in, the polymeric material and/or any solvent
in which the therapeutic agent and polymeric material are combined
prior to application to the electrode. For example, dexamethasone
acetate may be combined with silicone rubber to provide both an
immediate release of therapeutic agent from the surface of the
coating and an extended diffusion of therapeutic agent from the
remainder of the coating. This treatment may be further enhanced
because the agent is released from the coating at the point of
fixation.
[0034] FIG. 6 shows a flow-chart summarizing a method of preparing
and using embodiments of the present invention. First, a coating
mixture is prepared for application to the fixation electrode
(block 60).
[0035] In one embodiment, the coating mixture includes a
combination of uncured or cured polymer material, one or more
therapeutic agents, and an organic or substantially organic carrier
liquid. As used herein, the term "coating mixture" encompasses
solutions, dispersions, emulsions and other mixtures of solid
materials with one or more liquids. Examples of suitable carriers
for use in the coating mixture may include or contain Freon,
hexane, heptane and/or xylene. In another embodiment, certain
uncured polymers and therapeutic agents may be combined free of
solvent.
[0036] Generally speaking, the coating mixture may be applied as a
thin coating 46 to the fixation electrode. 40 or the polymer sleeve
50 by conventional methods, including dip, brush and spray
application (block 62). After applying of the coating mixture, the
solvent is dried or dispersed by heat or air-drying to form a thin
coating 46 (block 64). Optionally, the coating 46 may then be
partially or fully cured via known methods under conditions that do
not adversely affect the potency of the therapeutic agent. The
resulting coating 46 may have a thickness of between about 1 and
about 100 microns, more particularly between about 10 and about 80
microns, and even more particularly between about 13 and about 76
microns. The thickness of the coating may be increased by applying
multiple layers of the coating mixture. Such multiple coatings do
not necessarily need to utilize the same combination of polymer and
therapeutic agent in each layer. Instead, different polymers and/or
therapeutic agents could be utilized in discrete layers to provide
a desired therapeutic affect.
[0037] In one embodiment, the polymer sleeve 50 is first positioned
over a proximal portion of the electrode 40. The placement of the
polymer sleeve 50 may be accomplished by swelling the sleeve with a
suitable solvent, placing the polymer sleeve 50 over the electrode
40, and then drying the polymer sleeve 50. The coating mixture is
then applied onto the polymer sleeve 50 by brush application for
example, so that the proximal portion of the electrode 40 is coated
while the distal end of the electrode 40 remains uncoated and
exposed.
[0038] In an alternate embodiment, the polymer sleeve 50 is
positioned over most or all of the electrode 40. The entire polymer
sleeve 50 is then coated with the coating mixture by dip coating
for example. After the coating 46 has formed, a portion of the
resulting coating 46 and polymer sleeve 50 may be cut, stripped,
dissolved or otherwise removed to expose a desired portion of the
electrode 40.
[0039] In yet another embodiment, a portion of the electrode 40 is
covered with a conventional masking material. The coating mixture
may then be applied to the entire electrode 40 (with or without a
polymer sleeve 50 positioned over a portion of the electrode) by
dip application or another suitable application method. After the
coating 46 has formed, the masking agent may be removed to reveal
an exposed portion of the electrode 40.
[0040] In certain embodiments such as those illustrated in FIGS. 4
and 5, it may be desirable to leave exposed a portion of the
fixation electrode 40 other than the distal portion 26. In such
embodiments, the entire electrode 40 may first be covered with the
polymer sleeve 50. The coating mixture is then applied to the
entire polymer sleeve 50 via dip application or another suitable
application method. After curing, the desired portion of the
polymer sleeve 50 and the coating 46 is cut, stripped or otherwise
removed from the fixation electrode 40 to reveal an exposed
portion. A fixation electrode 40 having alternating exposed and
coated portions may be formed in a similar manner.
[0041] As further shown in FIG. 6, after coating, the lead 14 may
be implanted, as described with respect to FIG. 1, in a patient's
heart 16 (block 66). Specifically, the lead 14 of the present
invention may be suitable for implantation in the patient's
epicardium, endocardium or myocardium. Pacing therapy may then be
applied to the patient's heart in a conventional manner (block
68).
[0042] Various modifications and additions can be made to the
exemplary embodiments discussed without departing from the scope of
the present invention. Accordingly, the scope of the present
invention is intended to embrace all such alternatives,
modifications, and variations as fall within the scope of the
claims, together with all equivalents thereof.
* * * * *